[Endoperez]

I don't think it's a good idea to draw to many comparisons between real-world history and Dominions history. Gath shouldn't become Jews. Especially if there's any chance to have a Vampire Count named Adolf have anything near important position in the Ulm. And please, no rape in the backstory.

Regarding geography: just make it random. Have few neighbour-dependent quests that only appear if, say, Ulm and Marignon start next to each other. Even if you don't go that way, don't take it too seriously. The closest we're going to get is the Map That Will Never Be, and it will never be.

If you want to be serious about I, I suggest having MA Marignon without inquisitors influence France-equivalent while LA Marignon with diabolists/inquisitors influence Spain-equivalent.

Also, I don't think humans and giants ever breed with each other. The humans of Gath came from elsewhere (humanbreds, sibyls of Arcoscephale, some were close to Man, etc), and the giants grew smaller because the Nephilim bloodline became ever more and more diluted.